At present, silver halide photographic light-sensitive materials have been increasingly employed because of the highly excellent features such as high sensitivity, excellent gradation and the like as compared to the other printing materials. As methods for preparing a color proof in color plate-making and printing process, some methods have been known, that is, one method wherein color separation is performed by placing, on a color light-sensitive material, a film for preparing each of yellow, magenta, cyan and black plates which are prepared by color separation and inversion to dot, and another method wherein a light-sensitive material is subjected to direct dot-like exposure not through a film according to image data followed by development process. In recent years, the color proof has been increasingly employed not only for position-proofing to confirm characters and pictures but also for tone-proofing to confirm delicate shading and hue. In printing, printed dot become lager than those in the original on account of ink blot and the like. The size difference ratio is termed dot gain. The dot gain corresponds to the gradation in an ordinary photograph to affect remarkably image quality. Therefore, in order to prepare the high quality proof, it is required to adjust the dot gain to the similar level of prints. In the color proof preparing method employing a light-sensitive material, there have been known a method in which the dot gain is adjusted by regulating an amount of exposure. However, when the method is employed for a negative type light-sensitive material, variation in the exposure amount results in variation in density. Accordingly, when the dot gains are matched, the resulting density becomes out of the limit of a standard and when the densities are matched, the dot gain is out of the standard. In the case of a positive type, the increase in the dot gain has tended to deteriorate white background and image quality. Furthermore, a method has been known in which the dot gain is adjusted changing the sharpness of a light-sensitive material. In order to increase the dot gain, it is necessary to degrade the sharpness. When the sharpness is degraded, the reproduction of a large dot and a small dot is remarkably degraded. Accordingly, the method has had the limitation for the adjustment of the dot gain. In addition, as a means for adjusting the dot gain, a method has been known in which the gradation of a light-sensitive material is adjusted in an appropriate range. A method is advantageous in which especially, the gradation from the middle density to the low density is designed to be somewhat soft. However, when, in the conventional image-forming method, the gradation (toe gradation) from the middle density to the low density is designed so as to be in the optimum range for the adjustment of the dot gain, at the same time, the gradation (shoulder gradation) from the middle density to the high density tends to become soft and requires the increase in exposure amount necessary to obtain the maximum density. As a result, improvement has been required because problems are likely caused when the exposure amount is changes as described above.
Furthermore, in recent years, in accordance with the digitization of image information, an image-forming method has been increasingly employed in which a light-sensitive material is subjected to high intensity exposure for a short time such as 10.sup.-3 second or shorter followed by development process. In this case, just the same problem has been caused. Furthermore, in the high-intensity, short-time exposure, a phenomenon has been frequently observed in which a characteristic curve does not become a smooth S-letter type curve and at an exposure beyond a certain value, it bends sharply, resulting in a reduced density. Generally speaking, there is a limit for the range which is digitally controlled. When the aforementioned decrease in the shoulder gradation or bend of the characteristic cure are caused, it is difficult to hold the sufficient maximum density in the adjustable exposure range. When the maximum exposure amount is set so as to obtain the sufficient maximum density, the white background is likely degraded. It has been difficult to adjust the dot gain without causing the degradation of image quality.